In fact, on-board diagnostic systems—OBD systems—have for their main function the capacity to diagnose the presence of a fault in a propulsion component of the vehicle. OBD systems therefore consist in a set of hardware and software means for producing hardware diagnoses concerning the engine of vehicles.
The subject matter of the present invention concerns improving the operation of such OBD systems with the aim of increasing the relevance of the diagnoses produced.
In known manner, OBD systems hinge on on-board computers including strategies for monitoring or observation of the components of the engine in order to effect the most relevant possible fault diagnoses.
In practice, if a vehicle engine malfunctions, the dedicated computer detects the presence of a fault and the vehicle must be taken to a specialist mechanic for the latter to carry out investigations. First of all, the specialist mechanic will connect a computer to a special connector provided on the vehicle, generally referred to as the OBD connector, and use software to execute a method including a plurality of monitoring or observation strategies each adapted to process a plurality of components in order to produce the right diagnosis, consisting in designating the component responsible for the malfunction.
In fact, if a malfunction occurs in a vehicle, the objective of the OBD system is to determine the relevant fault. It is in fact crucial to produce the right diagnosis, which is complicated, notably if multiple malfunctions are detected, in order for the right component or components to be treated.
A fault in a component or a sporadic external event can sometimes generate the spurious detection of a malfunction in one or more other components that are not faulty, however. This is why the OBD system employs a fault management method able to filter the detected faults in order to retain only the relevant fault or at least a limited list of plausible faults.
Accordingly, in practice, if the OBD system detects a malfunction in a component, the corresponding fault is first considered intermittent. Following the application of a filtering strategy by the fault management method of the OBD system, the fault, if confirmed, is declared present and stored in a memory of the OBD system. The memory of the OBD system can subsequently be erased, either automatically or by a mechanic, when the fault is repaired or to carry out tests, for example.
Moreover, it is to be noted that particular attention is given to any fault affecting components liable to lead to a risk of increased pollution.
In fact, as a general rule, on-board diagnostics have become progressively more and more sophisticated, notably to enable engines to comply with increasingly strict statutory pollutant emission thresholds.
Thus sophisticated statutory requirements nowadays apply to motor vehicles and concern as much pollutant emission thresholds as methods and means to be employed to detect any failure of the ability to control those emissions and to alert the user to them.
These increasingly strict statutory requirements render optimum functioning of the OBD systems crucial.
In this context, as already mentioned, OBD systems employ fault management methods. Those methods include means generally referred to generically as FIM (Failure Interdependency Manager) means.
The fault management methods therefore consist mainly in a reaction strategy in the face of the faults detected, and in particular filtering of said detected faults in order, in the end, to flag only the relevant fault or a list of plausible faults. In other words, the fault management method employs monitoring or observation strategies adapted to produce diagnoses, said monitoring or observation strategies each monitoring a plurality of components in order, where applicable, to detect the presence of a fault in an engine component.
In practice, when a fault is detected as present, the effect of the diagnosis produced primarily causes the monitoring or observation strategy applied by the fault management method of the OBD system to order “fallback” to a reduced operating zone so as to ensure the operation of the minimum critical systems at the same time as protecting the engine components.
In the reduced operating zone, corresponding to a degraded mode of operation, the monitoring or observation strategies adapted to detect the presence of a fault can no longer function normally, and some diagnoses may no longer appear correctly. The monitoring or observation strategies monitoring a component for which a fault has been detected as present are in effect deactivated.
It is therefore crucial that the diagnostic strategies employed by the fault management method function optimally and that the calibration of all the hardware and software means of the OBD system is optimized accordingly.